The present invention relates to a pickup arm lifting device for use in a record player.
In general, the pickup or tone arms are provided with a device for providing the slow motion let-down for a stylus head or cartridge or lifting the stylus head away from the surface of a disk. This pickup arm lifting device comprises a housing, a slide shaft slidably fitted into the housing for vertical movement, a bias spring for normally biasing the slide shaft downward, a rotary shaft rotatably fitted into the housing for rotation about the axis perpendicular to the axis of the slide shaft, the rotary shaft being provided with a notched portion or cam semicircular in cross section with which engages the lower end of the slide shaft, and an operating lever attached to the end portion of the rotary shaft extended out of the housing. Upon rotation of the rotary shaft, the semicircular notched portion or cam forces the slide shaft to lift against the spring, thereby causing the pickup arm to lift away from the disk. Upon further rotation of the rotary shaft, the lower end of the slide shaft rides on the chord portion of the semicircular cam so that the slide shaft is lowered under the returning force of the bias spring. In general, the viscous oil is applied to the side surface of the slide shaft so that the slow motion let-down for cartridge is provided depending upon the viscosity of the oil and the returning force of the bias spring.
The conventional pickup arm lifting device with the above construction however has the following defects:
1. The semicircular notched or cam portion of the rotary shaft is in direct engagement with the lower end of the slide shaft to force it to rise. Therefore, when one rotates the operating lever too rapidly, the slide shaft is lifted too quickly so that the pickup arm bounces on a lift arm connected to the upper end of the slide shaft. This gives unpleasant sensations; and
2. Aging problem arises because the viscous oil leaks out of the gap between the slide shaft and the housing as well as the gap between the rotary shaft and the housing, and is vaporized. As a result, the pickup arm lifting device cannot provide a slow motion let-down for the cartridge, which is the most important function of the lifting device.